Television target tracking system

ABSTRACT

3. In a television type target tracking system a figure eight scan system comprising: a scan frequency oscillator for generating an output voltage, sin omega t, a frequency doubler circuit coupled to said scan frequency oscillator for generating a synchronized voltage, sin 2 omega t, television camera means including deflection coils and an imaging tube, circuit means coupling the output of said scan frequency oscillator and said frequency doubler as inputs to said deflection coils, vertical gate generator means having an input coupled to said scan oscillator and being triggered by the output sine wave of said scan oscillator near the zero value, horizontal gate generator means coupled to said scan oscillator through a 180* phase shifter and being triggered by the output sine wave of said scan oscillator near the zero value, tracking coincidence circuits coupled to the outputs of said vertical and horizontal gate generators and said television camera means for generating a first output signal representing the horizontal position of a target edge and a second output signal representing the vertical position of the target edge, and circuit means coupling said first and second output signals to the deflection coils of said television camera means.

Alpers TELEVISION TARGET TRACKING SYSTEM [75] Inventor: Frederick C.Alp'ers, Riverside,

Calif.

[73] Assignee: The United States of America as represented by theSecretary of the Navy [22] Filed: Dec. 29, 1969 [21] Appl. No.: 79,469

[52] US. Cl ..l78/6.8, l78/7.7, l78/DIG. 21

[51] Int. Cl. ..H04n 3/16 [58] Field of Search ..343/7.3; l78/6.8, 7.7

[56] References Cited UNITED STATES PATENTS 2,838,602 6/1958 Sprick....l78/6.8 2,939,909 6/1960 Toulon ..l78/6.8

Primary Examiner-Benjamin A. Borchelt Assistant Examiner-H. A. BirmielAtl0rneyJoseph M. St. Amand, Thomas M. Phillips and W. O. QuesenberryEXEMPLARY CLAIM 3. In a television type target tracking system a figureeight scan system comprising: a scan frequency oscillator for generatingan output voltage, sin wt, a frequency doubler circuit coupled to saidscan frequency oscillator for generating a synchronized voltage, sin 2wt, television camera means including deflection coils and an imagingtube, circuit means coupling the output of said scan frequencyoscillator and said frequency doubler as inputs to said deflectioncoils, vertical gate generator means having an input coupled to saidscan oscillator and being triggered by the output sine wave of said scanoscillator near the zero value, horizontal gate generator means coupledto said scan oscillator through a 180 phase shifter and being triggeredby the output sine wave of said scan oscillator near the zero value,tracking coincidence circuits coupled to the outputs of said verticaland horizontal gate generators and said television camera means forgenerating a first output signal representing the horizontal position ofa target edge and a second output signal representing the verticalposition of the target edge, and circuit means coupling said first andsecond output signals to the deflection coils of said television camerameans.

4 Claims, 11 Drawing Figures L; 29 I3 3h 32, R l TARGET /7 LENS ANDIMAGING K PROCESSING SCIENE F|| TERS TUBE PRE AMPL'F'ER AMPLIFIER lA (al B 9 I BEAM DEFLECTION FOCUSSING AND COILS 5:55:3

ALIGNMENT oR PLATES i P c G A VERTICAL RETRAcE HORIZONTAL TRACKING SWEEPCONTROL SWEEP LINE GATE GIENERATOR CIRCUIT GENERATOR GENERATOR I I I N22 IO 26 POWER RETRACE HORIZONTAL VERTICAL LINE-e TR'GGER i- TRIGGERSWEEP 'S SYN MIXER CLAMPER J 1 I f l9 2| 20 23 i PATENTEDJAN 16 I9753.711.639

SHEET 3 BF 8 FIG. 2 FIG. 5

FREDERICK C. ALPERS INVENTOK ATTORNEYS.

PATENTEDJAH 16 I975 3. 71 1. 639

SHEU HJF8 c: d 6 LL m o o m u. o I 1 x .1

FREDERICK C. ALPERS INVENTOR.

ATTORNEYS TELEVISION TARGET TRACKING SYSTEM The invention hereindescribed may be manufactured and used by or for the Government of theUnited States of America for governmental purposes without the paymentof any royalties thereon or therefor.

The present invention relates to television target tracking systems andmore particularly to television target tracking systems utilizingvertical retrace.

The present invention involves a means for deriving directionalinformation relative to a target by directing a television-type cameratoward a target scene, scanning the target scene by employing a rastersimilar to that used in the well-known television applications,processing video information gained from the camera system so as toderive a signal where changes in contrast occur (as at the edges of atarget), applying radar range type tracking techniques to track theseedge signals, and deriving voltages proportional to the position of thetarget in the raster through this edge tracking function. The particularsystem of this invention uses a chosen line in the normal televisionraster for a horizontal tracking function and uses a special verticalretrace of the beam through the raster between frames to give acorresponding vertical tracking line.

An object of the present invention is the provision of a televisiontarget tracking system which has an increased information rate andgreater accuracy than known systems.

Another object is to provide a television target tracking system whichprovides a special vertical retrace of the beam through the rasterbetween frames to give a corresponding vertical tracking line.

Other objects and many of the attendant advantages will become readilyappreciated as the same becomes better understood by reference to thefollowing detailed description when considered in connection with theaccompanying drawings wherein:

FIGS. 1A and 1B is a block diagram of one embodiment of the invention.

FIG. 2 shows the nature of the vertical retrace raster of FIG. 1.

FIG. 3 shows the principal waveforms involved.

FIGS. 4A and 4B is a block diagram of another embodiment of theinvention.

FIG. 5 illustrates the raster for the embodiment of FIG. 4.

FIGS. 6A and 6B is a block diagram of still another embodiment of theinvention.

FIG. 7 illustrates the raster for the embodiment of FIG. 6.

FIG. 8 illustrates the method by which the raster of FIG. 7 is obtained.

Referring now to the drawings wherein like reference charactersdesignate like or corresponding parts throughout the several views.There is shown in FIG. 1 in conjunction with FIGS. 2 and 3 the operationof one embodiment of the invention. There is shown in FIG. I ahorizontal sweep generator 10 and a vertical sweep generator 11.Normally horizontal sweep generator 10 is operated at a much higherrepetition frequency than vertical sweep generator 11 and in a typicalapplication the horizontal sweep generator might produce sawtoothwaveforms at approximately 15,000 cycles per second, while the verticalsweep generator produces such waveforms at approximately 60 cycles persecond. The faster sweep generator is made to affect scanning of thetelevision type camera in a horizontal direction for the sole reason ofconformance with conventional television systems. The output ofhorizontal sweep generator 10, waveform A, FIG. 3, is applied to thedeflection coils or plates 12 of imaging tube 13 of a television typecamera 15 to produce horizontal scan lines as shown in FIG. 2. Theoutput of horizontal sweep generator 10 is also connected as an input tosweep blanking circuit 14 which functions in the conventional televisionmanner to eliminate the horizontal retrace of the imaging tube beam. Theblanking voltage which serves this function appears as waveform B, FiG.3. THe output of vertical sweep generator 11 is shown as waveform C. Asshown, the output of horizontal sweep generator 10 is an uninterruptedsaw-tooth wave except during the recovery or retrace of the verticalsweep generator 11, waveform C. During this retrace, the output ofhorizontal sweep generator 10 is held at a constant value by techniqueswhich will be described later.

With reference to FIG. 3, waveform A from horizontal sweep generator 10is applied to horizontal positioning circuit 16, FIG. 1B, which developsan output pulse when the saw-tooth of waveform A rises to equal thevalue ofa voltage supplied to horizontal positioning circuit 16 fromhorizontal memory circuit 17. The output of horizontal positioningcircuit 16 is then utilized by horizontal tracking gate generator 18 toproduce a gating pulse shown as waveform D. Thus, there is one pulseoccuring in waveform D each time the output of horizontal sweepgenerator 16 increases to a voltage value equal to that supplied fromhorizontal memory circuit 17. Since horizontal sweep generator 10 isnormally a free-running circuit, vertical sweep generator 11 iscontrolled to operate in synchronism with a vertical trigger 19 which inturn may be synchronized to an available power line frequency if sodesired. Vertical trigger 19 has an output as shown in waveform E. Aretrace trigger mixer 21 uses coincidence between the output of triggerA, waveform E, and the occurrence of the output of repetition horizontaltracking gate 18, waveform D, to derive an output, waveform F, whichinitiates vertical retrace circuit 22 to produce waveform G, whichgoverns the duration as well as the initiation of the vertical retrace.The effective circuit action is then that horizontal tracking lines areproduced in the raster at a fixed rate until sufficient time has elapsedthat the scanning nears the bottom edge of the imaging tube, at whichtime a vertical trigger occurs. However, retrace action does not beginwith this vertical trigger but awaits the arrival of the horizontaltracking gate. By means which shall be explained later, the verticalretrace is then made to occur along the horizontal coordinate of therasteron which the target lies and thus the retrace passes through thetarget. With horizontal scanning clamped, retrace action continuesvertically through the raster until the top of the raster is reached, atwhich time horizontal scanning resumes and a new frame of the rasterbegins.

Choice of the particular scanning line used for horizontal tracking ismade in a line selector circuit 23 in the following manner: When theoutput of vertical sweep generator 11, waveform C, rises to a voltageequal to a voltage supplied from vertical memory circuit 24, waveform His then fed from line selector circuit 23 to tracking line gategenerator 26 which also receives a horizontal sweep signal from sweepblanking circuit 14 in the form of waveform B. Coincidence betweenwaveform H and one of the signals in waveform B initiates action oftracking line gate generator 26 and results in waveform I, which is madeto last slightly more than one horizontal scanning cycle. Waveform I islater used to permit horizontal tracking action only while it ispresent, and thus in effect it serves to select one particularhorizontal line in the raster for such tracking action. A verticaltracking gate, waveform j, is made to occur when waveform C falls(rather than rises) to a voltage equal to the voltage supplied by thevertical memory circuit 24. This action is effected by verticalpositioning circuit 27 and vertical tracking gate generator 28 whichfunction in a manner similar to horizontal positioning circuit 16 andhorizon tal tracking gate generator 18 described above.

The television type camera consists of a lens and filter system 29,imaging tube 13, a pre-amplifier 31, and a special processing amplifier32. The lens serves to focus an image of a target scene on the sensitiveface of imaging tube 13. Scanning of this face by the electron beamwithin the imaging tube then causes video signals to be generated whichare amplified by pre-amplifier 31, the output of which is a waveform,such as waveform K, depending upon the particular target scene which isviewed. Waveform K is fed through special processing amplifier 32 toproduce output signals, shown as waveform L, whenever a change in thelevel of the video signal occurs.

Horizontal tracking of an edge of the target represented by oneparticular pulse and waveform L is affected by a closed loop 25involving horizontal positioning circuit 16, horizontal tracking gategenerator 18, and horizontal memory circuit 17, plus delay network 33,left and right tracking coincidence circuits 34, 36 and horizontalcoincidence comparator 37. Tracking is initiated by a slew control (notshown) manipulated by an operator so that the gate position initiallycorresponds with an appropriate edge of the desired target. The slewcontrol is brought about by adjusting horizontal memory circuit 17 untilthe tracking gate comes at the desired spot along the horizontal scanline. A marker signal on a monitor oscilloscope aids the operator inperforming this function. This is accomplished while switches 42, 43 arein the alternate position, that is in the slew position.

During automatic horizontal tracking, which occurs after the operatorrelinquishes control of the tracking loop, horizontal tracking gate,waveform D and a slightly delayed (upon the order of one microsecond)form of this gate are applied to the left and right tracking coincidencecircuits 34, 36 respectively. Outputs of the coincidence circuits arecompared in horizontal coincidence comparator 37 which affects apositive correction in the horizontal memory circuit 17 output if thesignal from right tracking coincidence circuit 36 predominates, and anegative correction if the left tracking coincidence predominates.Coincidence of the undelayed tracking gate with the suitable target edgesignal of waveform L causes action of the tracking loop which results inpositioning the tracking gate further to the left to reduce thiscoincidence while a corresponding coincidence in the right trackingcoincidence circuit between that same edge signal of the waveform L andthe delayed tracking gate causes the opposite correction and motion ofthe tracking gate to the right. Hence, once tracking is initiated, theover-all action is that of causing tracking gate 30 and the delayed form30a (FIG. 2) thereof to straddle the chosen edge signal found in theoutput of processing.

amplifier 32. If the target tends to move to the left in raster,corrections are made which cause the gate to follow the target to theleft, and vice versa if the targets motion is to the right.

In producing the above tracking action, corrections are made in theoutput of horizontal memory circuit 17 which together with the initialsignal supplied thereto by the operator, keeps horizontal memory circuit17 output proportional to the horizontal coordinate of the position ofthe desired target edge in the raster. Thus, the output of thisparticular circuit serves as the horizontal output of the system whichmay be used as a control signal or may be recorded as a time record ofthe position of the target for instrumentation purposes. Verticalpositioning circuit 27, vertical tracking gate generator 28, delaynetwork 38, and vertical memory circuit 24, down and up trackingcoincidence circuits 39, 41 and vertical coincidence comparator 40perform the vertical tracking function in a similar manner as thatdescribed above for the horizontal tracking. In this tracking loopvertical tracking gate 55a and a delayed form 555 thereof are made tostraddle a signal representing the horizontal edge of the target, FIG.2, so that up and down tracking coincidence circuits 39, 41 effectcorrection in the vertical memory circuit output voltage and therebyyield a vertical output proportional to the vertical coordinate oftarget 35.

To assure that a horizontal tracking line is selected which occurs atthe same vertical coordinate as the vertical tracking gate which isfollowing the target through the vertical tracking loop action, the samevoltage which is used for the vertical positioning circuit in thevertical tracking loop is used for line selector circuit 23. Theequality of voltages which are used to define action of line selector 23and 'vertical positioning circuit 27, respectively, then relate to thesame reference voltage, the only difference being that one occurs duringthe slow rise of waveform C while the other occurs at the same voltageduring the relatively rapid retrace. Because target 35 has a definitesize, a strict identity of horizontal and vertical coordinates is notdesired and some small offset as shown in FIG. 2 is affected byintroducing fixed biases in horizontal and vertical tracking circuits.

In the systems of FIG. 4, the major portion of the raster which normallyserves to reconstruct an image of a target scene for benefit of anoperator .has been reduced for reasons of simplicity and only a singlehorizontal tracking line 47 and a vertical retrace line 48 (FIG. 5) havebeen retained. The tracking principals of this system are the same asthose of the system of'FIG. 1; i.e., horizontal tracking is obtained bya gating arrangement which straddles a vertical edge 49 of target 35 andvertical tracking by a similar arrangement strad- I dling horizontaledge 46, while the two tracking actions are interconnected to assurethat the tracking lines pass through target 35.

The primary difference between the system of FIG. 1 and the system ofFIG. 4 is that the system of FIG. 4 utilizes horizontal and verticalsweep circuits 50, 51, horizontal and vertical clamping circuits 52, 53and horizontal and vertical synchronizers 54, 56.

In the operation of the system of FIG. 4, vertical and horizontal sweepcircuits 50, 51 are saw-tooth generating circuits which operate in asimilar manner to horizontal sweep generator of FIG. 1. Horizontal sweepcircuit 50 rises to a peak value, causing the beam to scan horizontallyacross the raster and begins to fall off sharply in a normal saw-toothfashion for beam retrace. As the signal falls, it reaches a voltageequal to the horizontal output voltage from the horizontal trackingcircuit. Vertical trace synchronizer 54 compares the two voltages andgenerates a pulse when the two voltages are equal. The output pulse ofsynchronizer 54 is coupled to horizontal and vertical clamping circuits52, 53. This pulse initiates clamping of sweep circuit 50 so that thefall of the waveform from sweep circuit 50 is discontinued and theoutput is maintained constant. The same pulse reaching vertical clampingcircuit releases the clamping action of that circuit and allowspreviously clamped vertical sweep circuit 51 to complete its retrace anda new vertical saw-tooth waveform to begin. The vertical sweep circuitthen produces an output waveform which rises to a peak value, causing avertical scan across the raster, and begins falling off sharply forretrace again in the normal saw-tooth fashion. When the output voltageof vertical sweep circuit 51 falls to a value equal to the verticaloutput voltage from the vertical tracking circuit, horizontal tracesynchronizer generates an output pulse which is also supplied toclamping circuits 52, 53. this output pulse causes clamping of verticalclamping circuit 53 and releases horizontal clamping circuit 52 in thesame manner that the pulse from vertical trace synchronizer accomplishedthe opposite results. The resultant scanning action obtained by applyingthe vertical and horizontal sweep circuit outputs to the deflectioncoils or plates 12 of imaging tube 13 is then the two orthogonal sweeplines shown in FIG. 5. Tracking action is very much the same as that ofthe vertical retrace system of FIG. 1 with horizontal and verticaltracking loops yielding the horizontal and vertical output voltages.

Referring now to FIGS. 6, 7 and 8 which show the FIG. 8 scanning system.When tracking, target 35 is centered at the crossing point in the middleof the FIG. 8 and gate positions 57, 58 are adjusted to track the targetedges which are slightly off crossing point 59. Lines 60, 61 are made tocross at right angles to each other so that the scanning action acrosstarget 35 produces two orthogonal scanning lines.

The figure eight loop is formed by two sinusoidal signals applied atright angles to each other, as shown in FIG. 8. If the signal appliedalong an X axis is made equal to 2 sin wt while that along an orthogonalY axis is made equal to sin 2 mt, trigometeric considerations will showthat the resulting curve traced out as a function of time is expressedby the equation From this, the slope of the curve is:

At the crossover point:

5 X 0 and dy/dX =1 l,

which indicates that the crossover lines are orthogonal. To make thesecrossover lines coincide with normal horizontal and vertical axes, theXY reference system must be rotated through 45. The result is then thetrace 62 shown in Flg. 7.

In FIG 6, scan frequency oscillator 63 supplies the sin wt functionneeded for X-axis deflection. It also supplies a signal to frequencydoubler 64 which then generates a synchronized function, sin 2m, forY-axis deflection. The X and Y sinusoidal signals are applied directlyto deflection coils or plates 12 of tube 13 and these coils or platesare oriented at 45 to their normal axes so that the resultant crossbarfollows the normal horizontal and vertical directions as explainedabove. Phase shifter 65 is coupled between frequency double 64 anddeflection coils or plates 12 to cancel out any phase angle inherent inthe frequency doubler 64. To establish gate position at desired pointsin the figure eight raster, the output of oscillator 63 is used totrigger vertical gate generator 66 at a desired point near the zerovalue of the sine wave. The output of oscillator 63 is also passedthrough phase shifter 67, for approximately 180 phase shift, to triggerhorizontal gate generator 68. The biases of gate generators 66 and 68may be adjusted to move the gate position back and forth along the tracelines near the center of the raster until the desired positioning isachieved. Gates from gate generator 66 are coupled directly to downtracking coincidence circuit 39 and through delay network 69 to uptracking coincidence circuit 41. Gates from gate generator 68 arecoupled directly to right tracking coincidence circuit 36 and throughdelay network 71 to left tracking coincidence circuit 34. Horizontal andvertical tracking outputs are obtained in the same manner as describedin FIG. 1.

To assure the desired positioning of the figure eight scan in the image,correction signals are fed back to deflection coils or plates 12. Asumming amplifier 72 is provided to add the horizontal and verticaloutputs and differential amplifier 73 is provided to subtract thehorizontal and vertical outputs. The sum and difference signals areapplied to the deflection coils or plates 12 through a dc connectionwhereas the scan frequency from oscillator 63 and double scan frequencyfrom doubler 65 are applied through an ac connection. The result is thatboth sets of signals combine to control the position of the beam. Acorrection through the summing channel serves to move the figure eighttrace in either a horizontal or a vertical direction, depending on thepolarity of circuit connections and on the direction of the 45 rotationof the deflection coils. A correction signal from the differentialamplifier then causes motion of the figure eight trace in the orthogonaldirection to that caused by the summing amplifier output.

Obviously many modifications and variations of the present invention arepossible in the light of the above teachings. It is therefore to beunderstood that within the scope of the appended claims the inventionmay be practiced otherwise than as specifically described.

What is claimed is:

1. In a television type target tracking system a vertical retrace systemcomprising: raster generator means including a horizontal sweepgenerator and a vertical sweep generator; television camera meanscoupled to said horizontal and vertical sweep generators for generatingan output signal proportional to changes in contrast of its raster;blanking circuit means coupled to said horizontal sweep generator forblanking the horizontal retrace of said camera means; horizontal memorycircuit means having an output voltage proportional to the horizontalposition of a target in the scanning raster of said camera; horizontalpositioning circuit means coupled to said horizontal sweep generatormeans and to said horizontal memory circuit means for generating anoutput pulse when the output voltage of said horizontal sweep generatormeans rises to equal the value of the output voltage of said horizontalmemory circuit means; horizontal tracking gate generator means coupledto the output of said horizontal positioning circuit means forgenerating a gating pulse each time said horizontal positioning circuitmeans generates an output pulse; vertical trigger means having an inputcoupled to a reference voltage source for generating output pulses ofthe same frequency as said reference voltage, retrace trigger mixermeans coupled I to said vertical trigger means and to the output of saidhorizontal tracking gate generator for generating an output pulse uponthe coincidence between the output pulse of said vertical trigger meansand the output pulse of said horizontal tracking gate generator; retracecontrol circuit means coupled to said retrace trigger mixer means andsaid vertical sweep generator means for initiating and controlling theduration of the vertical retrace voltage of said vertical sweepgenerator; horizontal sweep clamping means coupled to said retracecontrol circuit means and to said horizontal sweep generator means forclamping the output of said horizontal sweep generator means for theduration of said vertical retrace voltage; vertical memory circuit meanshaving an output voltage proportional to vertical position of a targetin the scanning raster of said camera, line selector circuit meanscoupled to said vertical sweep generator means and to said verticalmemory circuit means for generating an output pulse when the outputvoltage of vertical sweep generator means rises to equal the output ofvertical memory circuit means; tracking line gate generator meanscoupled to the output of said line selector circuit means and to theoutput of said horizontal sweep generating means for generating anoutput pulse of a duration of slightly more than one horizontal scanningcycle upon the coincidence between the output pulse of line selectorcircuit means and the output of said horizontal sweep generating means;vertical positioning circuit means coupled to the output of saidvertical sweep generating means and to said vertical memory circuitmeans for generating an output pulse when the output voltage of verticalsweep generating means falls to a value equal to the output voltage ofsaid vertical memory circuit, vertical tracking gate generator meanscoupled to said vertical positioning circuit means for generating avertical gate upon the occurrence of an output pulse from said verticalpositioning circuit means, left tracking coincidence circuit meanshaving a first input coupled directly from said horizontal tracking gategenerator means and a second input coupled from said camera means forgenerating an output voltage proportional to coincidence of said firstand second inputs, right tracking coincidence circuit means having afirst input coupled to said horizontal tracking gate generator through afirst delay network, and a second input coupled from said camera meansfor generating an output voltage proportional to the coincidence of thefirst and second inputs applied thereto; horizontal coincidencecomparator means coupled to said left and right tracking coincidencecircuit means and to said horizon tal memory circuit means for causing arise in the output voltage of said horizontal memory circuit means whenthe output voltage of said right tracking coincidence circuitpredominates, and causing a decrease in the output voltage of saidhorizontal memory circuit means when the output of said left trackingcoincidence circuit means predominates; down tracking coincidencecircuit means having a first input coupled directly from said verticaltracking gate generator means and a second input coupled from saidcamera means for generating an output voltage proportional to thecoincidence of the first and second inputs coupled thereto, up trackingcoincidence circuit means having a first input coupled to said verticaltracking gate generator through a second delay network and a secondinput coupled from said camera means for generating an output voltageproportional to the coincidence of the first and second inputs appliedthereto; and vertical coincidence comparator means coupled to said upand down tracking coincidence circuit means and to said vertical circuitmeans for causing a rise in the output voltage of said vertical memorycircuit means when the output voltage of said up tracking coincidencecircuit predominates and causing a decrease in the output voltage ofsaid vertical memory circuit means when the output of said down trackingcoincidence circuit means predominates.

2. In a television type target tracking system a vertical retrace systemcomprising: raster generating means including a horizontal sweep circuitand a vertical sweep circuit; television camera means coupled to saidhorizontal and vertical circuits for generating an output signalproportional to changes in contrast of its raster; horizontal trackingcircuit means having an output proportional to the horizontal positionof a target in the raster of said camera means, vertical tracesynchronizer circuit coupled to said horizontal sweep circuit and tosaid horizontal tracking circuit for generating an output pulse when theoutput voltage of said horizontal sweep circuit falls to equal theoutput voltage of said horizontal tracking circuit; horizontal clampingcircuit means coupled to said vertical trace synchronizer circuit forinitiating clamping of said horizontal sweep circuit upon the occurrenceof an output pulse from the vertical trace synchronizer, verticalclamping circuit means coupled to said vertical trace synchronizer forunclamping said vertical sweep circuit, vertical tracking circuit meanshaving an output voltage proportional to the vertical position of atarget in the raster of said camera means, horizontal trace synchronizermeans coupled to said vertical sweep circuit and said vertical trackingcircuit means for generating an output pulse when the output voltage ofsaid vertical sweep circuit drops to a value equal to the output voltageof said vertical tracking circuit means, said horizontal clampingcircuit being responsive to the output pulse of said horizontal tracesynchronizer for unclamping said horizontal sweep circuit and saidvertical clamping circuit being responsive to the output pulse of saidhorizontal trace synchronizer for clamping said vertical sweep circuit.

3. In a television type target tracking system a figure eight scansystem comprising: a scan frequency oscillator for generating an outputvoltage, sin wt, a frequency doubler circuit coupled to said scanfrequency oscillator for generating a synchronized voltage, sin 2 wt,television camera means including deflection coils and an imaging tube,circuit means coupling the output of said scan frequency oscillator andsaid frequency doubler as inputs to said deflection coils, vertical gategenerator means having an input coupled to said scan oscillator andbeing triggered by the output sine wave of said scan oscillator near thezero value, horizontal gate generator means coupled to said scanoscillator through a 180 phase shifter and being triggered by the outputsine wave of said scan oscillator near the zero value; trackingcoincidence circuits coupled to the outputs of said vertical andhorizontal gate generators and said television camera means forgenerating a first output signal representing the horizontal position ofa target edge and a second output signal representing the verticalposition of the target edge, and circuit means coupling said first andsecond output signals to the deflection coils of said television camerameans.

4. the circuit of claim 3 wherein said tracking coincidence circuitscomprises: an up tracking coincidence circuit having a first inputcoupled to the output of said television camera means, a second inputcoupled through a delay network to the output of said vertical gategenerator and an output coupled as a first input to a verticalcoincidence comparator; a down tracking coincidence circuit having afirst input coupled to the output of said television camera means, asecond input coupled directly to the output of said horizontal gategenerator and an output coupled as a second input to said horizontalcoincidence comparator; a vertical memory circuit having an inputcoupled to the output of said vertical coincidence comparator and anoutput coupled as a first input to a summing amplifier and as a firstinput to a differential amplifier; a horizontal memory circuit having aninput coupled to the output of said horizontal coincidence comparatorand having an output coupled as a second input to said summing amplifierand as a second input to said differential amplifier; said summingamplifier having an output coupled as a first corrective input to saidtelevision camera means for providing horizontal and verticalcorrection; and said differential amplifier having an output coupled asa second corrective input to said television camera means for providingan orthogonal correction.

1. In a television type target tracking system a vertical retrace systemcomprising: raster generator means including a horizontal sweepgenerator and a vertical sweep generator; television camera meanscoupled to said horizontal and vertical sweep generators for generatingan output signal proportional to changes in contrast of its raster;blanking circuit means coupled to said horizontal sweep generator forblanking the horizontal retrace of said camera means; horizontal memorycircuit means having an output voltage proportional to the horizontalposition of a target in the scanning raster of said camera; horizontalpositioning circuit means coupled to said horizontal sweep generatormeans and to said horizontal memory circuit means for generating anoutput pulse when the output voltage of said horizontal sweep generatormeans rises to equal the value of the output voltage of said horizontalmemory circuit means; horizontal tracking gate generator means coupledto the output of said horizontal positioning circuit means forgenerating a gating pulse each time said horizontal positioning circuitmeans generates an output pulse; vertical trigger means having an inputcoupled to a reference voltage source for generating output pulses ofthe same frequency as said reference voltage, retrace trigger mixermeans coupled to said vertical trigger means and to the output of saidhorizontal tracking gate generator for generating an output pulse uponthe coincidence between the output pulse of said vertical trigger meansand the output pulse of said horizontal tracking gate generator; retracecontrol circuit means coupled to said retrace trigger mixer means andsaid vertical sweep generator means for initiating and controlling theduration of the vertical retrace voltage of said vertical sweepgenerator; horizontal sweep clamping means coupled to said retracecontrol circuit means and to said horizontal sweep generator means forclamping the output of said horizontal sweep generatoR means for theduration of said vertical retrace voltage; vertical memory circuit meanshaving an output voltage proportional to vertical position of a targetin the scanning raster of said camera, line selector circuit meanscoupled to said vertical sweep generator means and to said verticalmemory circuit means for generating an output pulse when the outputvoltage of vertical sweep generator means rises to equal the output ofvertical memory circuit means; tracking line gate generator meanscoupled to the output of said line selector circuit means and to theoutput of said horizontal sweep generating means for generating anoutput pulse of a duration of slightly more than one horizontal scanningcycle upon the coincidence between the output pulse of line selectorcircuit means and the output of said horizontal sweep generating means;vertical positioning circuit means coupled to the output of saidvertical sweep generating means and to said vertical memory circuitmeans for generating an output pulse when the output voltage of verticalsweep generating means falls to a value equal to the output voltage ofsaid vertical memory circuit, vertical tracking gate generator meanscoupled to said vertical positioning circuit means for generating avertical gate upon the occurrence of an output pulse from said verticalpositioning circuit means, left tracking coincidence circuit meanshaving a first input coupled directly from said horizontal tracking gategenerator means and a second input coupled from said camera means forgenerating an output voltage proportional to coincidence of said firstand second inputs, right tracking coincidence circuit means having afirst input coupled to said horizontal tracking gate generator through afirst delay network, and a second input coupled from said camera meansfor generating an output voltage proportional to the coincidence of thefirst and second inputs applied thereto; horizontal coincidencecomparator means coupled to said left and right tracking coincidencecircuit means and to said horizontal memory circuit means for causing arise in the output voltage of said horizontal memory circuit means whenthe output voltage of said right tracking coincidence circuitpredominates, and causing a decrease in the output voltage of saidhorizontal memory circuit means when the output of said left trackingcoincidence circuit means predominates; down tracking coincidencecircuit means having a first input coupled directly from said verticaltracking gate generator means and a second input coupled from saidcamera means for generating an output voltage proportional to thecoincidence of the first and second inputs coupled thereto, up trackingcoincidence circuit means having a first input coupled to said verticaltracking gate generator through a second delay network and a secondinput coupled from said camera means for generating an output voltageproportional to the coincidence of the first and second inputs appliedthereto; and vertical coincidence comparator means coupled to said upand down tracking coincidence circuit means and to said vertical circuitmeans for causing a rise in the output voltage of said vertical memorycircuit means when the output voltage of said up tracking coincidencecircuit predominates and causing a decrease in the output voltage ofsaid vertical memory circuit means when the output of said down trackingcoincidence circuit means predominates.
 1. In a television type targettracking system a vertical retrace system comprising: raster generatormeans including a horizontal sweep generator and a vertical sweepgenerator; television camera means coupled to said horizontal andvertical sweep generators for generating an output signal proportionalto changes in contrast of its raster; blanking circuit means coupled tosaid horizontal sweep generator for blanking the horizontal retrace ofsaid camera means; horizontal memory circuit means having an outputvoltage proportional to the horizontal position of a target in thescanning raster of said camera; horizontal positioning circuit meanscoupled to said horizontal sweep generator means and to said horizontalmemory circuit means for generating an output pulse when the outputvoltage of said horizontal sweep generator means rises to equal thevalue of the output voltage of said horizontal memory circuit means;horizontal tracking gate generator means coupled to the output of saidhorizontal positioning circuit means for generating a gating pulse eachtime said horizontal positioning circuit means generates an outputpulse; vertical trigger means having an input coupled to a referencevoltage source for generating output pulses of the same frequency assaid reference voltage, retrace trigger mixer means coupled to saidvertical trigger means and to the output of said horizontal trackinggate generator for generating an output pulse upon the coincidencebetween the output pulse of said vertical trigger means and the outputpulse of said horizontal tracking gate generator; retrace controlcircuit means coupled to said retrace trigger mixer means and saidvertical sweep generator means for initiating and controlling theduration of the vertical retrace voltage of said vertical sweepgenerator; horizontal sweep clamping means coupled to said retracecontrol circuit means and to said horizontal sweep generator means forclamping the output of said horizontal sweep generatoR means for theduration of said vertical retrace voltage; vertical memory circuit meanshaving an output voltage proportional to vertical position of a targetin the scanning raster of said camera, line selector circuit meanscoupled to said vertical sweep generator means and to said verticalmemory circuit means for generating an output pulse when the outputvoltage of vertical sweep generator means rises to equal the output ofvertical memory circuit means; tracking line gate generator meanscoupled to the output of said line selector circuit means and to theoutput of said horizontal sweep generating means for generating anoutput pulse of a duration of slightly more than one horizontal scanningcycle upon the coincidence between the output pulse of line selectorcircuit means and the output of said horizontal sweep generating means;vertical positioning circuit means coupled to the output of saidvertical sweep generating means and to said vertical memory circuitmeans for generating an output pulse when the output voltage of verticalsweep generating means falls to a value equal to the output voltage ofsaid vertical memory circuit, vertical tracking gate generator meanscoupled to said vertical positioning circuit means for generating avertical gate upon the occurrence of an output pulse from said verticalpositioning circuit means, left tracking coincidence circuit meanshaving a first input coupled directly from said horizontal tracking gategenerator means and a second input coupled from said camera means forgenerating an output voltage proportional to coincidence of said firstand second inputs, right tracking coincidence circuit means having afirst input coupled to said horizontal tracking gate generator through afirst delay network, and a second input coupled from said camera meansfor generating an output voltage proportional to the coincidence of thefirst and second inputs applied thereto; horizontal coincidencecomparator means coupled to said left and right tracking coincidencecircuit means and to said horizontal memory circuit means for causing arise in the output voltage of said horizontal memory circuit means whenthe output voltage of said right tracking coincidence circuitpredominates, and causing a decrease in the output voltage of saidhorizontal memory circuit means when the output of said left trackingcoincidence circuit means predominates; down tracking coincidencecircuit means having a first input coupled directly from said verticaltracking gate generator means and a second input coupled from saidcamera means for generating an output voltage proportional to thecoincidence of the first and second inputs coupled thereto, up trackingcoincidence circuit means having a first input coupled to said verticaltracking gate generator through a second delay network and a secondinput coupled from said camera means for generating an output voltageproportional to the coincidence of the first and second inputs appliedthereto; and vertical coincidence comparator means coupled to said upand down tracking coincidence circuit means and to said vertical circuitmeans for causing a rise in the output voltage of said vertical memorycircuit means when the output voltage of said up tracking coincidencecircuit predominates and causing a decrease in the output voltage ofsaid vertical memory circuit means when the output of said down trackingcoincidence circuit means predominates.
 2. In a television type targettracking system a vertical retrace system comprising: raster generatingmeans including a horizontal sweep circuit and a vertical sweep circuit;television camera means coupled to said horizontal and vertical circuitsfor generating an output signal proportional to changes in contrast ofits raster; horizontal tracking circuit means having an outputproportional to the horizontal position of a target in the raster ofsaid camera means, vertical trace synchronizer circuit coupled to saidhorizontal sweep circuit and to said horizontal tracking circuiT forgenerating an output pulse when the output voltage of said horizontalsweep circuit falls to equal the output voltage of said horizontaltracking circuit; horizontal clamping circuit means coupled to saidvertical trace synchronizer circuit for initiating clamping of saidhorizontal sweep circuit upon the occurrence of an output pulse from thevertical trace synchronizer, vertical clamping circuit means coupled tosaid vertical trace synchronizer for unclamping said vertical sweepcircuit, vertical tracking circuit means having an output voltageproportional to the vertical position of a target in the raster of saidcamera means, horizontal trace synchronizer means coupled to saidvertical sweep circuit and said vertical tracking circuit means forgenerating an output pulse when the output voltage of said verticalsweep circuit drops to a value equal to the output voltage of saidvertical tracking circuit means, said horizontal clamping circuit beingresponsive to the output pulse of said horizontal trace synchronizer forunclamping said horizontal sweep circuit and said vertical clampingcircuit being responsive to the output pulse of said horizontal tracesynchronizer for clamping said vertical sweep circuit.
 4. the circuit ofclaim 3 wherein said tracking coincidence circuits comprises: an uptracking coincidence circuit having a first input coupled to the outputof said television camera means, a second input coupled through a delaynetwork to the output of said vertical gate generator and an outputcoupled as a first input to a vertical coincidence comparator; a downtracking coincidence circuit having a first input coupled to the outputof said television camera means, a second input coupled directly to theoutput of said horizontal gate generator and an output coupled as asecond input to said horizontal coincidence comparator; a verticalmemory circuit having an input coupled to the output of said verticalcoincidence comparator and an output coupled as a first input to asumming amplifier and as a first input to a differential amplifier; ahorizontal memory circuit having an input coupled to the output of saidhorizontal coincidence comparator and having an output coupled as asecond input to said summing amplifier and as a second input to saiddifferential amplifier; said summing amplifier having an output coupledas a first corrective input to said television camera means forproviding horizontal and vertical correction; and said differentialamplifier having an output coupled as a second corrective input to saidtelevision camera means for providing an orthogonal correction.